Chronic renal failure associated with vesico-ureteral reflux related nephropathy, either primary or associated with obstructive uropathy, accounts for as many as 30% of patients with end stage renal disease. Whether corrective surgery or prophylactic therapy of urinary tract infection represents the best approach to the prevention of renal damage remains controversial. The study described, based on random allocation of patients with Grade IV vesico-ureteral reflex (International Classification) to either medical of surgical therapy, will permit us to compare the effect of each of these therapeutic modalities on a) rate of renal growth, b) development of new scars, c) progression of established scars, d) emergent rates of recurrent infections, e) incidence of hypertension. Well defined methods of patient selection and of initial and follow-up radiological and functional examination, established the permise for generation of meaningful information. Since the study is confined to Grade IV reflex (International Classification) in children less than 10 years old and excludes duplicate collecting systems, the potential patient pool is limited to less than 10% of the reflux population. To generate statistically significant data in a reasonable time frame, collaboration between large numbers of referral centers both in the United States and Europe is necessary. A common protocol, an international administrative structure and an identical data management system have been developed. During the first 4 years of the study, 280 patients have been recruited from 16 institutions in the USA and 8 in Europe. It is anticipated that the total required number of 175 patients in each treatment group will be reached by December 31, 1984. This population will be followed for the five year period for which support is requested. The results will be analyzed both on separate and pooled data.